Selective gas phase filter material

ABSTRACT

An improved tobacco smoke filter material is formed from a porous particulate carrier impregnated with an additive having an affinity for volatile smoke acids and aldehydes, such as buffered polyethyleneimine, wherein the carrier particles have a pore diameter from 0.1 to 2.0 microns, a surface area of from about 1 to 15 square meters per gram, and a pore volume no less than about 0.3 cubic centimeter per gram.

United States Patent 91 Litzinger [451 Feb. 13, 1973 SELECTIVE GAS PHASEFILTER MATERIAL [75] Inventor: Elmer Francis Litzinger, Louisville,

[73] Assignee: Brown & Williamson Tobacco Corporation, Louisville, Ky.

[22 Filed: se czs, 1970 [21] Appl. No.1 75,773

[52] US. Cl ..l31/267 [51] Int. Cl. ..A24b 15/02, A24d 1/06 [58] Fieldof Search....13l/10 R109, 265, 267, 269

[56] References Cited UNITED STATES PATENTS 3,434,479 3/1969 Till et a1...13'l/10.9

11/1968 Walker etal ..131/267 9/1967 Horsewell et a1 ..131/269 X PrimaryExaminerJoseph S. Reich Assistant Examiner-George M. YahwakAttorney-Kane, Dalsimer, Kane, Sullivan and Kurucz ABSTRACT 9 Claims, NoDrawings about 0.1 to 2.0 microns.

SELECTIVE GAS PHASE FILTER MATERIAL This'application is related toco-pending application Ser. No. 75,772, filed Sept. 25, 1970.

BACKGROUND OF THE INVENTION The invention is related to a tobacco smokefilter material. In particular, it is related to a porous particulatematerial for selectively removing smoke acidsand aldehydes. Hitherto, ithas been proposed to disperse 1 various materials, such as amines and/oramine salts, on conventional filter tows (see U.S. Pat. No. 3,410,282)to selectively remove smoke acids from tobacco smoke. Similarly, it hasbeen proposed in US. Pat. No.

3,340,879 to treat conventional filter tow with a poly(alkyleneimine) toselectively removesmoke acids while allowing a major proportion of theflavorants to pass. Additionally, it has been proposed in U.S. Pat.

No. 2,815,760 toadsorb specified amines on certain porous'granules ofunspecified pore diameter, surface SUMMARY OF THE INVENTION selectedvolatile components have been removed, such.

as vapor phase aldehydes, while leaving in the smoke desired flavor oraroma imparting materials.

The above and other beneficial objects and ad vantages are obtained inaccordance with the present invention by an improved tobacco smokefilter material which comprises a porous particulate carrier impregnatedwith an additive having an affinity for volatile smoke acids andaldehydes, wherein each of the said carrier particles has a pore'diameter of from about 0.l to 2.0 microns, a surfacearea offrom about Ito square meters per gram and a pore volume no less than -about0.3cubic'centimeterper gram. It has been should be no less than about 0.3cubic centimeter per gram (cc/gm). Below this level selective removal ofsmoke stream acids and, particularly, aldehydes is significantlydiminished. While applicant does not wish to be bound to any particulartheory, it is nevertheless postulated that as increasing amounts ofadditive are deposited on the substrate, pore filling occurs. Toovercome this defect,it has been found that the porous carrier shouldhave a pore volume of no less than 0.3 cubic centimeter per gram, whensufficient loadings of additive are incorporated on the carrier toeffectively reduce smoke acids and aldehydes.

Porous carriers with the above pore sizes and pore volumes have surfaceareas in the range from about I to 15 square meters per gram (m /gm).This is to be contrasted with conventional commercial adsorbentmaterials with surface areas of greater than 200 square meters per gram.Such commercial materials have been found to be relatively poorsubstrates for the additive described herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The additive employed shouldhave an affinity for volatile acids and aldehydes entrained in a tobaccosmoke stream. The additive may be an amine at least partially bufferedby a carboxylic' acid. The carboxylic acid salts are prepared byreacting primary or secondary alkyl and hydroxyalkyl amines with theacid. Some amines which have been found particularly effective include:ethylamine, dibutylamine, ethylenediamine,

I ethanolamine and the like. The acids used in the found that bufferedpoly(alkylcneimines) supported on i a porous alumina substrate havingthe aforesaid physical characteristics provide highly efficient filterm' ateri- 'als for the selective removal of volatile aldehydes, such asacetaldehyde and, acrolein, from cigarette smoke.

Such materials also retain their normal affinity forsmoke acids.

Th'ephysical parameters of the substrate material are of criticalimportance. In order to provide substantial reductions of vapor phasealdehydes, for example, it is necessary that the average pore diameter(assuming cylindrical pores) of the substrate material be from In orderto achieve satisfactory loadings of additive on the substrate, the porevolume of the substrate preparation of the amine salts can be aliphaticor aromatic monoor polycarboxylic acids including the following: acetic,itaconic, lactict succinic, benzoic and cinnamic acids. I

Other carbonyl reactive materials which may be employed'as additivesinclude phenylhydrazine, semicarbazide, thiosemicarbaz ide and thelike.-

The porous car-rier for the additive can be any solid substrate capableof supporting the additive provided that the carrier has the previouslyspecified dimensionalparameters. In general, organic and inorganicmaterials may be employed. Typical carriers, also referred toherein assubstrates, include: magnesite, zeolites, fullers earth diatomaceousearth, polyethylene granules, silica gel, and the like.

Examplesof the filter material of the invention are produced by at leastpartially neutralizing each of the following organic bases with any ofthe following acids and,'thereafter, depositing the buffered additive onany of the following substrates:

Organic Base propylaziridine) diatomaceous earth it is preferred toemploy at least partially buffered poly(alkyleneimines) as an additivefor the substrate. Preferred poly(alkyleneimines) are disclosed in U.S.Pat. No. 3,340,879 and, accordingly, the disclosure of the aforesaidpatent is expressly incorporated herein. The poly(alkyleneimines) are atleast partially neutralized or buffered with a carboxylic acid.Generally, alkanoic acids are preferred for this purpose.

. For best results, poly(ethyleneimine), at least partially bufferedwith acetic acid, is employed.

When acid-buffered filter material is employed, al-

' dehyde filtration efficiency is generally acceptable, as

long as the pH range of the additive is between about 6.0-and 7.6. Inthe case of the highly preferred additive, poly(ethyleneimine) bufferedwith acetic acid, it has been found that the optimum pH is 7.4.

Enhanced results are obtained .with'and,'accordingly, it is preferred toemploy a particulate porous alumina as the substrate for the additive ofthe invention. A particularly preferred alumina is produced by calciningthe trihydrate at high temperatures (usually between about l,100 to1,300 Centigrade). v

The particularly preferred filter materials of the invention are formedby buffering to a pH in the range from about 6.0 to 7.6 any of thefollowing poly(alkyleneimines) V having the general formula: NH (CR CRCNH),.l-l where each R is individually selected from the class consistingof hydrogen, lower alkyl radicals free from aliphatic unsaturationandhavingfrom one to six carbon atoms and n is a'whole number greater than12, with any one ofthe following 'alkanoic acids and ,then. combiningthebufferedadditive with a porous alumina:

' I Porous Alumina Calcine Temp. Alkanoic (degrees Acid Cent.

Pore Diameter (microns) Pore I Vol.

Surface 'Area mlgm) poly(alkyleneimine) butyric ll 1.5 0.5

valcric l300 l.l 0.4.

caproic glutaric dimethyl- 3-n-pr0- pylaziridine) succinic Generally,for effective selective treatment of tobacco smoke according to theinvention, at least about 2 percent by weight of additive based on theweight of the carrier is deposited on the carrier. Usually no more thanabout 6 percent by weight of additive is employed. Increasing theloading of additive has the effect of filling the pores of the carrier,thereby reducing selective removal of smoke stream components.

In the case of the preferred poly (alkyleneimines) buffered withalkanoic acids to a pH in the range from 6.0 to 7.6 and deposited on aporous alumina substrate of the invention, it has been found that from 4to 6 percent by weight buffered poly(alkyleneimines) yields enhancedresults.

The buffered additives are deposited on the above porous substrates byconventional techniques, for example, by immersing the carrier in thesolution in which the additive has been prepared and, thereafter,evaporating the solvent. The substrate is then dried and formed into afilter.

Alternatively the filter material can be made in situ by atleastpartially neutralizing one of the above compounds with one of theabove acids in the presence of a porous carrier.

in general, sufficient quantities of the filter material of theinvention are employed in smoking articles to significantly reduce thequantity of volatile components normally present in tobacco smoke and,par

ticularly, hydrogen cyanide, acetaldehyde and acrolein. For this andother purposes,- it is preferred to employ from about to milligrams offilter material in a filter for use in smoking articles, such ascigarettes.

vln one embodiment, a filter is prepared by encasing the filter materialof the invention in an outer wrapper. The resulting filter may beemployed alone or in combination with conventional cellulose acetatefilters. Triple filters employing, sequentially, the following filtersections: cellulose acetate, the filter material of the invention andcellulose acetate, have proven particularly workable. The filtermaterial may be used in conjunction with perforated cigarette paper, ifdesired, or filter ventilation means may be employed. In anotherembodiment, the filter material may be dispersed, in granular form,either on paper or cellulose acetate tow and encased in an outerwrapper.

The following examples are provided to further illustrate the nature ofthe invention and are not limitative of scope. I

EXAMPLE I In order to illustrate the effectiveness of the filtermaterial of the invention, an additive was prepared by bufferingpoly(ethyleneimine) with acetic acid to pH of 7.4. The amount ofaceticacid used for this adjustment was 1.5 milliequivalents of acidvper gram of poly(ethyleneimine). I

The resulting buffered additive was deposited on selected poriusaluminas. Their physical charac-. I

teristics are set forth in the following table:

For sample A, percent by weight of the buffered additive was depositedon the porous alumina substrate. Filter material was prepared fromsampleB by depositing, respectively, 2 and 5 percent by weight of the additiveon the porous alumina. For sample C, 2 percent by weight of additive wasdeposited on the porous alumina Predetermined quantities of the filtermaterial were packed into 8 millimeter cavities between 7 and 6millimeter lengths of conventional cellulose acetate filters of 84millimeter cigarettes (tobacco sections 63 millimeters in length). Theresulting cigarettes were smoked to 28 millimeter butt lengths on aconstant vacuum smoking machine taking 35 milliliter puffs of 2 secondsduration at one minute intervals.

In the following table, the weight of the, filter 'material is expressedin .milligrams. The filter efficiency represents the weight percent ofcomponent trapped by the filter materials based on the total amount ofthe component enteringthe cigarette filter. I

SELECTIVE FILTRATION EFFICIENCIES The above table illustratestheefficiency with which volatile components, particularly aldehydiccomponents, are removed from tobacco smoke, employing the filtermaterials of the invention. Similar results are obtained when otheradditives having an affinity for volatile vapor phase acids andaldehydes are deposited upon porous particulate carriers, whereinthe'carrier particleshave a'pore diameter of from about 0.1 to 2.0microns, a surface area from about 1 to square meters per gram and apore volume no less than about 0.3 cubic centimeters per gram.

In the following'table any of the additive materials having an affinityfor'vapor phase acids and aldehydes may bedeposited upon any of theporous carriers having the aforesaidphysical characteristics to form thefilter material of the invention, with similar results.

Additive The effect Qfdifferent loadings of filter material on vaporphase acids and aldehydes was examined by depositing 5 percent byweight, polyethyleneimineacetate buffered, on a porous alumina substrateand diluting the resulting material with untreated alumina in a 13millimeter filter bed joined with an 8 millimeter cellulose acetatefilter. The dual filter was joined to a tobacco cylinder and testedaccording to the procedure of Example I.

The results set forth in the following table illustrate filterefficiencies of four different'porous aluminas, each deposited with 5percent by weight of the above additive, wherein the mean pore diameterof the alumina carriers was in the range of from 0.1 to L8 microns. Porevolume and surface area were within the critical ranges.

Effect of Additive Loading on Filter Efficiency Treated Hydrogenalumina-weight Cyanide Acetaldehy de Acrole in (milligrams) removedremoved) removed) 50 56-63 0-l5 l6-28 I00 60-7l 21-34 33-38 I50 -7733-47 41-46 As is evident from the above table, for substantial aldehydereductions, at least about milligrams of treated carrier per filter arerequired. Similar results are obtained for other additives deposited onthe porous carriers described herein.

COMPARATIVE EXAMPLE I Effect of Pore Size on Filtration Efficiency POREDIAMETER Weight of Additive on Pore Volume Pore Diameter AcetaldehydeAlumina (cc/gm) (microns) removed From this table, it is seen thatremoval of vapor phase aldehydes is reduced when the pore diameter ofthe porous carrier is less than 0.1 microns and more than 2.0 microns.

PORE VOLUME Weight of Surface Pore Pore Acetal- Acrolcin Additive AreaVolume Diameter dehyde reon alumina (mi/gm) (cc/gm) (microns) removedmoved 5% LI 0.2 0.8 56 48 5% 1.1 0.4 l.] 67 78 As is seen from theresults of the above tests, when pore volume is reduced below about 0.3cc per gram then filtration efficiency for vapor phase aldehydes isundesirably reduced. Note that during the above tests,

both the surface area and pore diameter of the substrate were maintainedwithin permissible limits.

SURFACE AREA Weight of Surface Pore Hydrogen Acctal- Additive on AreaVolume Cyanide dehyde I Alumina (m /gm) (cc/gm) rcmoved% removed Fromtheabove, it is seen that when the surface area of the porous carrier isgreater than about 15 square meters per gram, then vapor phasefiltration is advcrsely affected. Similar results are obtained belowabout i m /gm.

Similar filtration effects with respect to vapor phase components arenoted when other porous carriers described herein are employed with theaforesaid physical characteristics.

COMPARATIVE EXAMPLE II In order to further illustrate the enhancedselective filtration results obtained, aporous alumina, calcined at atemperature of 1300Centigrade having a surface area of 1.1 square metersper gram, a pore volume of 0.4 cubic centimeters per gram and a porediameter of 1.1 microns was employed. To a portion of the porous aluminawas added 5 percent by weight poly(ethyleneimine), unbuffered. Toanother portion of the porous alumina was added 5% by weight poly-(ethyleneimine) buffered with acetic acid to a pH of 7.4. Anotherportion of the calcined alumina was treated with percent by weightpoly(ethyleneimine) buffered with acetic acid. The resulting filtermaterials wereformed into filters and testedfor vapor phase efficiency:according to Example l. The following results were obtained:

Acrolein 10% acetatc buffcred 3i v additive From the above table, it isseen that untreated porous alumina had no measurable effect on vaporphase, deliveries. With unbuffered poly(ethyleneimine) (PEI') there issome reduction in vapor phase aldehydes. A

' substantial reduction in vapor phase aldehydes is obtained when apoly( alkyleneimine), buffered to a pH of from about 6 to 7.6 with analkanoic acid, is employed on porous alumina substrate.

Filter material prepared from buffered PEI and deposited on conventionalpaper, sections ofqdual paper-cellulose acetate filters was also testedfor vapor phase component removal. It was found that only about 25percent acetaldehyde was selectively removedfrom cigarette smokeemploying the dispersed additive.

The synergism observed between the additive and the porous carrierillustrated hereinabove is obtained when other additives and poroussubstrates of the invention are employed in place of the bufferedpoly(ethyleneimine) additive deposited on the porous alumina substrate.As shown above, when the quantity of additive deposited on the porouscarrier is adjusted above about 6 percent by'weight, aldehydicreductions in tobacco smoke significantly decrease. It is postulatedthat the pores of the substrate become filled by the excess additive,thereby reducing the affinity of the filter material for the vapor.phase components in tobacco smoke.

This invention is not to be limited except as set forth in the followingclaims. Having thus described my invention, what is claimed 1. Animproved tobacco smoke filter material comprising at least mg. of aporous particulate carrier impregnated with a poly(alkyleneimine)alkanoate, wherein from about 2 to 6 percent by weight alkanoate isdeposited on the carrier based on the total weight-of the alkanoate andcarrier, said poly(alkyleneimine) alkanoate having a pH from about 6.0to 7.6, and wherein each of said carrier particles has a pore diameterof from about 0.1 to 2.0 microns, a surface area of from about 1 to 15square meters per gram and a pore volume no less than about 0.3 cubiccentimeter per' gram.

2. The invention in accordance with claim 1 in which the carrier is aporous alumina.

3. The tobacco smoke filter of claim 1 wherein the pH of thepoly(alkyleneimine) is buffered to about 7.4 with acetic acid. I

4. An improved filter adapted to be affixed to a cigarette andcomprising, in combination: a filter outer wrap having a tubularconfiguration and an inner filler formed from a .plurality of particlesformed from a porous particulate carrier impregnated with an alkanoicacid buffered poly(alkyleneimine) additive, said additive buffered to apH from about 6.0 to 7.6, from about 2 to 6 percent by weightadditivedeposited on the 'carrier based on the total weight of carrier andadditive, wherein from about 100 to milligrams of filler are employed insaid filter and wherein the carrier particles each'have a pore diameterfromabout 0.1 to 2.0 microns, a surface area of from about 1 to 15square meters per gram and a pore volume no less than about 0.3 cubiccentimeter per gram.

5. An improved tobacco smoke filter material'comprising at least 100 mg.of a porous particulate carrier impregnated-with a poly(alkyleneimine)buffered with an alkanoic acid to a pH from about 6.0 to 7.6, whereinfrom about 2 m6 percent by weight buffered poly(alkyleneimine) isdeposited on the carrier based on the total weight of the bufferedpoly(alkyleneimine) and carrier and wherein the carrier particles eachhave a pore diameter from about 0.1 to 2.0 microns, a surface area offrom about 1 to 15 square meters per gram and a pore volume no less thanabout 0.3 cubic centimeter per gram.

6. An improved tobacco smoke filter material adapted to be affixed to acigarette and comprising: at least 100 milligrams of a porous aluminaimpregnated with poly(ethyleneimine) buffered to a pH of 7.4 with aceticacid, wherein the porous alumina has a pore diameter of from about 0.1to 2.0 microns, a surface area of from about 1 to square meters pergram, a pore volume of from 0.3 to 0.8 cubic centimeter per gram andwherein from about 4 to 6 percent by weight buffered poly(ethyleneimine)is deposited on the porous alumina.

7. An improved filter adapted to be affixed to a cigarette andcomprising, in combination: a filter outer wrap having a tubularconfiguration and an inner filler formed from a plurality of particlesformed from at least 100 milligrams of a porous particulate carrierimpregnated with a poly(alkyleneimine) buffered with an alkanoic acidwherein from about 2 to 6 percent by weight acid bufferedpoly(alkyleneimine) is deposited on the carrier base on the total weightof the poly(alkyleneimine) and carrier, said poly(alkyleneimine) beingbuffered to a pH from about 6.0 to 7.6 and having an affinity forvolatile smoke aldehydes and acids, wherein the carrier particles eachhave a pore diameter from about 0.1 to 2.0 microns, a surface area offrom about 1 to 15 square meters per gram and a pore volume no less thanabout 0.3 cubic centimeter per gram.

8. The invention in accordance with claim 7 in which the carrier is aporous alumina.

9. The invention in accordance with claim 8 wherein the additive ispoly(ethyleneimine) buffered to a pH of about 7.4 with acetic acid andwherein from 4 to 6 percent by weight of poly(ethyleneimine) isdeposited on the porous alumina.

UNITED STATES PATENT @FFKCE 1110-2 14A QERTWMATE GE RWTHN Patent No. 3716 O63 Dated February 13 1973 I t Elmer Francis Litzinger It iscertified that 'error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

At Col. 3, line 40, "NI-I (CR CRC NH) H" should be --NH (CR CR NH) H7Col. 5, second chart, there should be a space between the third andfourth lines and a space between the fifth and sixth lines;

Col. 7, line 54, after "buffered" add--additiVe---; and

line 56, delete "additive".

Signed and sealed this 3rd day of July 1973.

(SEAL) Attest:

EDWARD M.FLETCHERI,JR. v Rene Tegtmeyer Attesting Officer ActingCommissioner of Patents FORM PO-1050 (10-69) -oc 375.p 9

- u S. GOVERNMENT PRINTING OFFICE: I969 o356-334

1. An improved tobacco smoke filter material comprising at least 100 mg.of a porous particulate carrier impregnated with a poly(alkyleneimine)alkanoate, wherein from about 2 to 6 percent by weight alkanoate isdeposited on the carrier based on the total weight of the alkanoate andcarrier, said poly(alkyleneimine) alkanoate having a pH from about 6.0to 7.6, and wherein each of said carrier particles has a pore diameterof from about 0.1 to 2.0 microns, a surface area of from about 1 to 15square meters per gram and a pore volume no less than about 0.3 cubiccentimeter per gram.
 2. The invention in accordance with claim 1 inwhich the carrier is a porous alumina.
 3. The tobacco smoke filter ofclaim 1 wherein the pH of the poly(alkyleneimine) is buffered to about7.4 with acetic acid.
 4. An improved filter adapted to be affixed to acigarette and comprising, in combination: a filter outer wrap having atubular configuration and an inner filler formed from a plurality ofparticles formed from a porous particulate carrier impregnated with analkanoic acid buffered poly(alkyleneimine) additive, said additivebuffered to a pH from about 6.0 to 7.6, from about 2 to 6 percent byweight additive deposited on the carrier based on the total weight ofcarrier and additive, wherein from about 100 to 150 milligrams of fillerare employed in said filter and wherein the carrier particles each havea pore diameter from about 0.1 to 2.0 microns, a surface area of fromabout 1 to 15 square meters per gram and a pore volume no less thanabout 0.3 cubic centimeter per gram.
 5. An improved tobacco smoke filtermaterial comprising at least 100 mg. of a porous particulate carrierimpregnated with a poly(alkyleneimine) buffered with an alkanoic acid toa pH from about 6.0 to 7.6, wherein from about 2 to 6 percent by weightbuffered poly(alkyleneimine) is deposited on the carrier based on thetotal weight of the buffered poly(alkyleneimine) and carrier and whereinthe carrier particles each have a pore diameter from about 0.1 to 2.0microns, a surface area of from about 1 to 15 square meters per gram anda pore volume no less than about 0.3 cubic centimeter per gram.
 6. Animproved tobacco smoke filter material adapted to be affixed to acigarette and comprising: at least 100 milligrams of a porous aluminaimpregnated with poly(ethyleneimine) buffered to a pH of 7.4 with aceticacid, wherein the porous alumina has a pore diameter of from about 0.1to 2.0 microns, a surface area of from about 1 to 15 square meters pergram, a pore volume of from 0.3 to 0.8 cubic centimeter per gram andwherein from about 4 to 6 percent by weight buffered poly(ethyleneimine)is deposited on the porous alumina.
 7. An improved filter adapted to beaffixed to a cigarette and comprising, in combination: a filter outerwrap having a tubular configuration and an inner filler formed from aplurality of particles formed from at least 100 milligrams of a porousparticulate carrier impregnated with a poly(alkyleneimine) buffered withan alkanoic acid wherein from about 2 to 6 percent by weight acidbuffered poly(alkyleneimine) is deposited on the carrier base on thetotal weight of the poly(alkyleneimine) and carrier, saidpoly(alkyleneimine) being buffered to a pH from about 6.0 to 7.6 andhaving an affinity for volatile smoke aldehydes and acids, wherein thecarrier particles each have a pore diameter from about 0.1 to 2.0microns, a surface area of from about 1 to 15 square meters per gram anda pore volume no less than about 0.3 cubic centimeter per Gram.
 8. Theinvention in accordance with claim 7 in which the carrier is a porousalumina.